Field of the Invention
The present invention relates to a foldable display device including a display panel that is capable of being folded or unfolded when it is used.
Discussion of the Related Art
There are various kinds of display devices for displaying images, for example, liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light-emitting diode (OLED) display devices, electrophoretic display (EPD) devices, etc.
Recently, studies on foldable display devices, which are bendable or foldable and can therefore be used in a greater variety of applications, have been actively conducted.
A foldable display device can be configured by connecting flat display panels, or can be configured to include a display panel having flexibility, that is, a flexible display panel.
A flexible display panel refers to a display panel that is pliable, bendable, foldable, or rollable like paper, while maintaining the display characteristics of general flat display panels.
The flexible display panel can be configured to include a plastic substrate that is deformable by external pressure.
The plastic substrate can have a structure in which a base film is coated on both surfaces thereof with a barrier coating. The base film can be formed of various kinds of resin such as, for example, polyimide (PI), polycarbonate (PC), polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), or fiber-reinforced plastic (FRP). The barrier coating can be applied on two opposite surfaces of the base film. An organic film or an inorganic film can be used as the barrier coating in order to maintain flexibility.
The flexible display panel is capable of being rolled or folded into various shapes due to its flexibility. A flexible display device, to which the flexible display panel is applied, requires a case for protecting the flexible display panel and various other components accommodated in the case. Thus, the flexible display device faces many problems that should be overcome in order to realize deformability by which the entire display device is capable of being deformed or shaped into any desired shape.
On the other hand, a foldable display device can be configured to be folded and unfolded with a relatively simple mechanical structure.
The foldable display device generally includes a flexible display panel and a housing for allowing the flexible display panel to be maintained in a predetermined shape or at a predetermined folding angle.
In order to allow the flexible display panel to be maintained in a predetermined shape or at a predetermined folding angle, the housing of the foldable display device includes a hinge mechanism, by which the housing is folded at a portion thereof corresponding to the folding region of the flexible display panel. In general, the housing includes two flat plates that are hinged to each other by a central hinge, and realizes a folding operation through pivoting movement of the two flat plates about the hinge.
However, when the two flat plates of the housing pivot about the hinge for the folding operation, the ends of the two flat plates, which are contiguous to and face each other in the unfolded state, move away from each other during the folding operation, and thus the folding region of the housing becomes partially open when the folding operation is completed.